Catalytic combustion in general has many advantages compared to conventional gas phase combustion. The most obvious advantages are the very low emissions, high safety (normally no flame is present and the gas mixture is too lean for gas phase ignition), controllability, wide power range and silent operation. Typical disadvantages are the requirements of complete fuel evaporation and homogenous air/fuel mixture to eliminate the risk for thermal degradation of the catalyst. Due to the fuel evaporation requirement, combustion of gaseous fuels presents fewer challenges than liquid fuel combustion and the commercial applications are increasing. However, when it comes to catalytic combustion of liquid fuels there are still few, if any, commercial applications due to the problem to achieve complete and efficient evaporation of hydrocarbon fuels without accumulation of heavy hydrocarbon residues. Furthermore, there is a need for a fast and low-emission start-up principle for such a process, consuming a minimum of electrical energy.
The problem with evaporation of liquid fuels lies in the fact that the evaporator temperature must be controllable depending on the operating conditions of the burner and accumulation of heavy hydrocarbon residuals must be prevented in order to avoid coking. Furthermore, the evaporator must reach a suitable temperature in short time during start-up in order to obtain a fast and efficient start-up process improving performance and minimizing cold start emissions. Finally, this has to be accomplished with minimal energy consumption.